This application claims a priority based on Japanese Patent Application 11-261135 filed on Sep. 14, 1999, and 2000-233091 filed on Aug. 1, 2000, the entire contents of which are incorporated herein by reference for all purposes.
The present invention relates to a technique for creating a dynamic image representing a motion of an object.
Techniques referred to as xe2x80x9cmotion blur xe2x80x9d are known as a technique for creating the dynamic image representing the motion of an object.
According to motion blur techniques, when a dynamic image comprising a series of image frames is created, an image of an object drawn in at least one past image frame is also drawn in the current image frame in which the image of the object is drawn. Alternatively, the image of the object is also drawn at a position, which is shifted from the current drawing position in a direction toward the drawing position in the past image frame in the current image frame in which the image of the object is drawn.
Those motion blur techniques make it possible to represent a lively motion of the object by representing after-images of the moving object with high quality.
However, when the dynamic image includes a multiplicity of moving objects, a processing volume of an apparatus for creating the dynamic image may exceed an allowable range according to the motion blur techniques. For example, in the case of the apparatus which must create and display a three-dimensional computer graphics animation in real time, e.g., a video game apparatus which provides an interactive three-dimensional computer graphics animation, an excessive processing volume may make it impossible to provide a proper three-dimensional computer graphics animation in real time.
On the other hand, when the drawing size of the object is small, a high quality representation, which is achieved by the motion blur techniques, does not necessarily contribute to improvement of the quality of the dynamic image as a whole.
The present invention was made taking the above-described situation into consideration, and it is an object of the invention to create a dynamic image representing a motion of an object with a reduced volume of processing.
In order to achieve the above-described object, according to the present invention, there is provided a method of creating image frames forming a dynamic image obtained by shooting a virtual object which is moving with predetermined motion characteristics, the method having:
a coordinate calculating step which calculates a position of the object in the current image frame according to the motion characteristics;
a history accumulating step which accumulates a history of the position calculated at the coordinate calculating step; a drawing step which draws in the current image frame the object at the position calculated at the coordinate calculating step; and
a locus drawing step which draws in the current image frame a line segment or a shape so as to connect a plurality of positions including the position calculated at the coordinate calculating step and at least one position accumulated at the history accumulating step in order of those positions starting from the position calculated earlier.
According to the present invention, a locus of the position of the object is represented by drawing a line segment or shape connecting a plurality of positions in the history of the position of the object, i.e., a plurality of positions on the locus of the object. This makes it possible to represent the locus of the object with a quite small processing load in a quite short processing time compared to those in conventional techniques such as motion blur. When the locus is drawn in such a manner as being more transparent, the older is the position in its history, a unique beautiful locus can be represented.